The invention relates to a direct current (DC) voltage detection stick for non-contacting detection of a direct current in a wire by using the capacitance of air.
Electrical voltage sticks are known in the art for both detecting alternating current (AC) and direct current (DC). The prior art voltage sticks may require that a needle is inserted through the plastic protection cover of the cable and into the metal wire to be able to detect the DC voltage. This leaves a permanent damage of the wire cover and water and other contaminants may enter into the opening after the needle has been withdrawn. This a particular problem in automobiles and other equipment that are operated in rain and snow conditions and have an electrical system that is powered a battery such as 12 or 24 VDC. Other DC testing devices rely on a relatively unreliable electromagnetism system for detecting cables carrying a DC current.
The present invention is a device and a method for detecting a direct current by using the capacitance in the air. The receiver has a casing member and a tip is removably attached to the casing member. A sensor is disposed within the casing member for sensing the presence of a transmitter signal when the sensor is positioned adjacent to an electrically conductive member carrying a direct current. An indicator and an integrated circuit is disposed within the casing member. The integrated circuit that may act as a first filter and a power source are disposed within the casing member for powering the sensor, the indicator and a first integrated circuit. A transmitter is connected to a direct current generating power source and the transmitter produces a transmitter signal by periodically connecting a resistance R to the battery. Preferably, the transmitter signal has a frequency of about 20 kHz. During detection, the tip is placed adjacent to, but not in contact with, the electrically conductive member to take advantage of the capacitance in the air disposed between the sensor and the electrically conductive member. Due to the period load on the battery, the sensor may sense the electrical field created between the two opposite poles of the battery. The detected transmitter signal is passed through the integrated circuit to filter out all frequencies except the desired 20 kHz and a direct current detection signal is sent to the indicator to activate the indicator.